This invention relates generally to integrated gasification combined cycles (IGCC) and, more particularly, to an acid gas removal (AGR) system to be used with an IGCC.
At least some known integrated gasification combined cycles use gasification to breakdown biomass feedstock to create synthetic gas (syngas) for use in a turbine engine. Moreover, steam produced during operation of the IGCC is used to operate a steam turbine. As such, known IGCCs can operate at efficiencies approaching 60%. After gasification, known IGCCs generally use an acid gas removal system to remove sulfur from the syngas created in the gasifier, thereby creating a low sulfur syngas that may be useable in the turbine engine.
More specifically, to remove sulfur from the syngas, at least some known IGCCs couple an absorber downstream from the gasifier. The absorber contains a solvent capable of absorbing hydrogen sulfide and carbonyl sulfide from the syngas, such that a sulfur-rich solvent is created. The sulfur-rich solvent is delivered to a stripper, wherein acid gases are removed from the solvent such that a sulfur-lean solvent can be recirculated to the absorber. The acid gases are then channeled to a sulfur recovery unit wherein a usable sulfur product is produced along with gases which can be recirculated to the gasifier.
At least some known acid gas removal systems may be incapable of meeting current emissions requirements during all operating conditions. For example, high sulfur start-up fuels may produce a large quantity of emissions. While many of the emissions generated are captured during the acid gas removal process, at least some emissions may be released into the atmosphere during system shutdowns, equipment failures, or sulfur recovery unit trips.
One known method to facilitate reducing emissions is to utilize low sulfur start-up fuels or methanol. However, such systems generally require additional inventory and handling equipment, which increase the costs associated with the IGCC. Other known systems include a start-up absorber to facilitate absorbing the syngas immediately following gasification. However, the solvents used in such an absorber typically operate at a low temperature and require low temperature syngas. As such, a start-up absorber is infeasible in at least some known systems. Moreover, known start-up absorbers are only capable of reducing emissions upstream from the acid gas removal system, but in many systems, emissions may be generated downstream from the acid gas removal system.